As a structure for improving a cell breakdown voltage and on-resistance of a power MOSFET having a trench type field plate electrode structure, a structure in which a field plate electrode is embedded in a stripe shaped trench is known. In addition, in order to reduce the on-resistance, a power MOSFET having a column trench type field plate structure in which a field plate electrode is formed in a column shape to reduce an ineffective region where an on current does not flow, is known.
However, in the stripe trench type field plate structure, the distance between the field plate electrodes is constant, and in the column trench structure, the distance between the field plate electrodes tends to be non-uniform and there is a problem that the breakdown voltage of the device is lowered.